Method of sealing vuggy regions in well bores



c. cosHow 3,318,378

METHOD OF SEALING VUGGY REGIONS IN WELL BORES May 9, 1967 Filed March 25, .1964

PIC-3.2.

FiG.l.

INVENTOR Chester L.Coshow BY 61mm ATTORNEY United States Patent 3,318,378 METHOD OF SEALING VUGGY REGIONS IN WELL BORES Chester L. Coshow, 1113 Center St., Collinsville, Okla. 74021 Filed Mar. 23, 1964, Ser. No. 353,891

1 Claim. (Cl. 166--4) This invention relates generally to the art of well drilling and more particularly to a method of sealing a subsurface vuggy formation encountered in the course of the well boring operation.

In accordance with usually known well drilling practices, the circulation of water into and from the bore as the drill bit is caused to rotate therein, serves to clear the bore of residual materials thus facilitating continued drilling and further provides a drilling fluid which lubricates and minimizes strain on the drill. Accordingly, it is essential that mud returns, i.e., the residue and water suspension, be continually flowing through the flow return line of the circulation system.

Where a well is being drilled into substrata comprised primarily of rock formations, it is not uncommon that vuggy regions, i.e., rock formations containing cavities which are lined, but incompletely filled, with mineral matter, are encountered. Vuggy regions, in view of their porosity, undesirably permit loss of circulating water therethrough, and hence interfere with the well drilling operation. The length of the bore extending through the vuggy region is referred to herein as a lost circulation zone, such nomenclature being precisely descriptive of the inherently detrimental property thereof.

Consonant with the foregoing, it will be appreciated that the obviation of water and mud seepage through a lost circulation zone must be accomplished as a prerequisite to further drilling, the method of effectuating such obviation being the primary object of the present invention.

Another object of the instant invention resides in the provision of a method capable of precluding loss of circulation within a well bore, such preclusion being-accomplished without the application of a casing about the bore extending through a vuggy region.

A further object of this invention is to provide a method of packing the vugs of a lost circulation zone with lostcirculation-material.

A still further object of the present invention lies in the sealing of a lost-circulation-zone by searing the exposed surface of a well bore extending therethrough.

Other objects and advantages of the invention will become apparent to one skilled in the art by dint of the following disclosure of said invention taken in conjunction with the accompanying drawings, wherein FIGURE 1 is a vertical cross-sectional view of a well boring operation showing the drill bit within the bore extending beyond the lower extremity of a lost-circulation-zone;

FIGURE 2 is a view of the bore illustrated in FIGURE 1, the drill bit being withdrawn therefrom and lostcirculation-rnaterial and an explosive charge being positioned longitudinally of the lost-circulation-zone;

FIGURE 3 is a fragmentary view ,of the bore wherein the explosive charge is being detonated; and

FIGURE 4 is a view of the segment of the bore shown in FIGURE 3 following detonation of the explosive charge.

As shown in FIGURE 1 of the drawings, a well bore 2 is being drilled subsurfacedly of rock formation 3, drill bit 4, held by collar 6, being rotated by drill pipe 8. As the pipe, collar and bit are rotated while supported by rig 10, water and mud is circulated into and from the bore, pump 12 being effective to cause such circulation.

Where, as concerns the instant invention, the bore is being formed through a rock substrata, steel, cement or like casings are not required for placement about the bore inasmuch as a closed system containing the circulating water and materials suspended therein is ordinarily provided by the impermeable rock-lined wall surface 12 of the bore. Occasionally, however, loss of such circulation is occasioned by porosity in the wall surface at 13 due to vuggy regions or formations r14 into which mud is lost thus creating a lost-circulation-zone 16 which must be sealed prior to continuation of the drilling procedure.

Observation of a decrease in circulating returns indicates penetration of the bore through a vuggy region and thus serves to determine the location of the lost-circulation-zone. Drilling is continued a short distance beyond the zone as seen in FIGURE 1 notwithstanding the absence of further returns, and the flow of water into the bore is then curtailed. The pipe, collar and drill are withdrawn from the bore, whereafter lost-circulationrmaterial 18, e.g., cotton seed hulls, walnut hulls, palco wool, mixtures of the foregoing or other suitable material or mixture, is introduced into the bore whereby the material is caused to extend the length of the lost-circulation-zone 16 and beyond the upper and lower extremities 20, 22, thereof, respectively. Such introduction of the lost-circulation-material is preferably accomplished through open-ended drill pipe 8 which has been replaced into the bore after drill bit 4 and collar 6 have been removed therefrom. Subsequent to loading the lost-circulation-zone with said material, the drill pipe is removed.

An explosive charge 24, comprised of any suitable explosive, e.g., nitro-glycerine, dynamite, etc., is then positioned substantially centrally and longitudinally of the lost-cinculation-material 18, and said charge preferably extending, as shown, beyond the upper and lower extremities of the zone 16. The charge 24 is preferably suspended by a line 26 which is guided by pulley wheels 28 and 30 for controlled winching from unit 32. It will be understood that detonation of the charge may be accomplished by time, pressure or other suitable mechanism connected directly to the charge, or remote detonation may be accomplished, whereupon line 26 may be formed of or include conducting cables :Capable of carrying electrical energy to the charge, the source of said energy being e.g., within unit 32, and detonation of the charge bein g eifectu-ated at said unit.

The charge is then detonated as illustrated in FIGURE 3 of the drawings, the effect, as shown in FIGURE 4, being to shatter the vuggy formation contiguous with the immediate impact of the blast and thus compact the fractured constituents of the formation to form a wall as indicated by numeral 34. The surface 36 of the compacted wall is glazed or fused by the heat of the explosion; the lost-circulation-material 18 being also completed behind said wall at 37 to provide a seal intermediate wall 34 and the glazed surface thereof and the outlying vuggy region containing lost mud as indicated at 38.

Following the sealing of the vuggy region in accordance with the afore-described method, water circulation may then be resumed and drilling of the bore may be continued until the desired depth is established. In the event, however, another lost-.circulation-zone is encountered, the foregoing sealing procedure is repeated, such being accomplished as often as required,

Obviously, the explosive rate of the charge utilized will be varied as will the type and magnitude thereof, depending upon the diameter and length of the zone to be sealed.

Inasmuch as changes may be made in carrying out the above method without departing from the scope of the invention, it is intended that all matter contained in the instant disclosure be interpreted as illustrative and exemplary and not in a limiting sense. Accordingly, such variations falling within the purview of this invention may be made while within the spirit of the invention and without sacrificing any of theattendant advantages thereof, provided, however, that such changes fall within the scope of the claim appended hereto.

What is claimed is:

In a well drilling procedure, the method of sealing vuggy regi-onszencountered in the course of said procedure, comprising the steps of drilling a bore subsurfaoedly of a rock formation, circulating water. within said =bore during the drilling thereof, determining the location of a vuggy region upon observing loss of the circulating water, drilling beyond the vuggy region, curtailing water circulation, Withdrawing the drill from the bore, placing an open-ended drill pipe into the bore, introducing lo st-vcir culation-material into the bore through. said open-ended drill pipe whereby said material extends the length of said vuggy region and beyond the upper and lower extremities thereof, positioning a suitable explosive charge substantially centrally and longitudinally of said lost-circulation-material, detonating said charge thereby compacting said m'aterial surfacedly of said vuggy region and by the heat derived through the detonation of said explosive charge fusing the combined exposed surf-ace and 1ostcircula-tionmaterial compacted therein, resuming water circulation and drilling of the bore until the desired depth is established.

References Cited by the Examiner UNITED STATES PATENTS CHARLES E. OCONNELL, Primdry Examiner.

2o JACOBL NACKENOFF, Examiner.

N. C. BYERS, Assistant Examiner. 

